TRILL Working Group Radia Perlman
INTERNET-DRAFT EMC
Intended status: Informational Donald Eastlake
Mingui Zhang
Huawei
Anoop Ghanwani
Dell
Hongjun Zhai
JIT
Expires: January 4, 2016 July 5, 2015
Alternatives for Multilevel TRILL
(Transparent Interconnection of Lots of Links)
<draft-perlman-trill-rbridge-multilevel-10.txt>
Abstract
Extending TRILL to multiple levels has challenges that are not
addressed by the already-existing capability of IS-IS to have
multiple levels. One issue is with the handling of multi-destination
packet distribution trees. Another issue is with TRILL switch
nicknames. There have been two proposed approaches. One approach,
which we refer to as the "unique nickname" approach, gives unique
nicknames to all the TRILL switches in the multilevel campus, either
by having the level-1/level-2 border TRILL switches advertise which
nicknames are not available for assignment in the area, or by
partitioning the 16-bit nickname into an "area" field and a "nickname
inside the area" field. The other approach, which we refer to as the
"aggregated nickname" approach, involves hiding the nicknames within
areas, allowing nicknames to be reused in different areas, by having
the border TRILL switches rewrite the nickname fields when entering
or leaving an area. Each of those approaches has advantages and
disadvantages. This informational document suggests allowing a choice
of approach in each area. This allows the simplicity of the unique
nickname approach in installations in which there is no danger of
running out of nicknames and allows the complexity of hiding the
nicknames in an area to be phased into larger installations on a per-
area basis.
Status of This Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79. Distribution of this document is
unlimited. Comments should be sent to the TRILL working group
mailing list <trill@ietf.org>.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
R. Perlman, et al [Page 1]INTERNET-DRAFT Multilevel TRILL
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R. Perlman, et al [Page 2]INTERNET-DRAFT Multilevel TRILLTable of Contents
1. Introduction............................................4
1.1 TRILL Scalability Issues...............................4
1.2 Improvements Due to Multilevel.........................5
1.3 Unique and Aggregated Nicknames........................6
1.3 More on Areas..........................................6
1.4 Terminology and Acronyms...............................7
2. Multilevel TRILL Issues.................................8
2.1 Non-zero Area Addresses................................9
2.2 Aggregated versus Unique Nicknames.....................9
2.2.1 More Details on Unique Nicknames....................10
2.2.2 More Details on Aggregated Nicknames................11
2.2.2.1 Border Learning Aggregated Nicknames..............12
2.2.2.2 Swap Nickname Field Aggregated Nicknames..........14
2.2.2.3 Comparison........................................14
2.3 Building Multi-Area Trees.............................15
2.4 The RPF Check for Trees...............................15
2.5 Area Nickname Acquisition.............................16
2.6 Link State Representation of Areas....................16